In some mobile bodies, such as vehicles, a plurality of controllers are disposed therein in order to control an engine and a transmission, which are also provided in the mobile body, and data signals are communicated between the controllers to this end. An example of a communication device to be used with the aforesaid controllers is shown in FIG. 6. In FIG. 6, reference numeral 302 denotes a first or engine controller for controlling an engine (not shown); 304 a second controller or drive system controller for controlling an automatic transmission (not shown); and, 306 a communication device between the engine controller 302 and the drive system controller 304.
At least first and second data output means, more specifically, a water temperature sensor 308 and an air conditioner (A/C) 310 are provided and connected to the engine controller 302 through first and second signal lines, more specifically a water temperature signal line 312 and an air-conditioning signal line 314, respectively. In addition, the engine controller 302 is linked to different data output means other than the water temperature sensor 308, that is, various sensors (not shown) for outputting other data signals indicative of a throttle opening, the number of engine revolutions and the like.
The water temperature sensor 308 feeds a water temperature signal into the controller 302 by way of a first data signal. The water temperature signal is a signal providing information on how the engine is running. The air-conditioner 310, which is driven by the engine, delivers a drive information signal, i.e., an air-conditioning on/off signal, to the controller 302 by way of a second data signal.
The engine controller 302 has the function of entering thereinto the water temperature signal from the sensor 308, the air-conditioning signal from the air conditioner 310, and other data signals, and then feeding the same signals into the drive system controller 304 at the following step. The engine controller 302 provides control over engine ignition timing and fuel in response to the entered water temperature signal and other data signals, while effecting control over activation and deactivation of the air conditioner 310 in accordance with the air-conditioning signal.
Turning now to FIGS. 7 and 8, the aforesaid water temperature signal is converted into duty value "T1" when being delivered to the drive system controller 304 from the engine controller 302. The duty value varies with water temperature. More specifically, such a converted signal is entered into the drive system controller 304 at any value within predetermined range "R", which range is defined by upper limit "TU" (e.g., 26.6 milliseconds) and lower limit "TL" (e.g., 9.81 milliseconds). FIG. 8 shows an overall duty cycle of a water temperature output (WTO) having a value T of 32.7 milliseconds corresponding to 30.6 Hz.
The engine controller 302 determines the presence or absence of abnormalities such as failures of the water temperature sensor 308 and/or the air conditioner 310 as well as disconnection of the water temperature signal line 312 and/or the air-conditioning signal line 314 on the basis of the entered data signals such as the water temperature signal and/or the air-conditioning signal. When a determination is made that such abnormalities are present, then the engine controller 302 feeds first and second abnormal signals into the drive system controller 304 at the next step. The first abnormal signal is a water temperature abnormal signal representing an abnormal state of the water temperature sensor 308, while the second abnormal signal is an air-conditioning abnormal signal indicating an abnormal state of the air conditioner 310, as described in detail hereinafter.
The data signals are output and communicated from the engine controller 302 to the drive system controller 304 through the communication device 306. The communication device 306 allows the engine controller 302 to be linked to the drive system controller 304 through first, second, and third communication lines which are a water temperature communication line 316, an air-conditioning communication line 318, and an air-conditioning abnormality communication line 320, respectively.
The communication device 306 permits the water temperature and air-conditioning signals to be entered into the drive system controller 304 from the engine controller 302 through the water temperature communication line 316 and the air-conditioning communication line 318. The drive system controller 304 provides gearshift control and slip control in accordance with the entered water temperature signal and air-conditioning signal. The gearshift control changes an engaged state of an auxiliary gearshift mechanism in the automatic transmission, while the slip control brings a lock-up clutch into semi-clutch engagement.
When the engine controller 302 determines, according to the water temperature signal, that the water temperature sensor 308 is in an abnormal state, then the communication device 306 allows the above-mentioned water temperature abnormal signal defined by the equation XDTHWHNF=1 to be fed into the drive system controller 304 through the water temperature communication line 316.
At this time, the water temperature abnormal signal is entered into the drive system controller 304 at any value beyond the aforesaid predetermined range "R". More specifically, the same abnormal signal is fed into the drive system controller 304 through the water temperature communication line 316 at lower limit-lessened value "TL.sub.L " beyond the predetermined range, which value is less than lower limit "TL", as illustrated by a broken line in FIG. 7.
Further, when the engine controller 302 determines, according to the air-conditioning signal, that the air conditioner 310 is in an abnormal state defined by the equation XDTHWLNF=1, then the communication device 306 allows the above-mentioned air-conditioning abnormal signal to be fed into the drive system controller 304 through the air-conditioning abnormality communication line 320.
Examples of the above-described communication device are disclosed in published Japanese Patent Application Laid-Out Nos. 5-263710, 5-233577, and 7-69093.
A device according to the aforesaid Application No. 5-263710 includes first and second central processors. The first central processor calculates a drive amount of an actuator, and transmits a fail signal when a failure occurs. The second central processor controls the actuator in accordance with data of the drive amount which is sent from the first central processor. When abnormalities occur, then the first central processor transmits data as the fail signal to the second central processor, which data indicates a drive amount exceeding a limit of the drive amount of the actuator.
Another device according to the above Application No. 5-233577 includes at least three central processors and a fail communication line and a help communication line. One of the above processors is a main central processor, while the remainder are subordinate central processors. The above communication lines are disposed between the main processor and the subordinate processors for communicating a fail signal. When abnormalities occur, then the central processor sends the fail signal to the main processor, which in turn communicates the occurrence of the abnormalities to the subordinate processors through the aforesaid communication lines.
A further device according to the above Application No. 7-69093 is a failure-diagnosing device including first and second operational state-detecting means and first and second controllers for diagnosing failures which occur in either the detecting means or the controllers. The failure-diagnosing device is characterized by a first failure-detecting means, a first failure signal output means, a second failure-detecting means, a second failure signal output means, a converting means, and a determining and diagnosing means.
In the communication device 306 as shown in FIG. 6, when the water temperature sensor 308 is abnormal, then the water temperature abnormality signal is communicated to the drive system controller 304 through the water temperature communication line 316.
However, an inconvenience is encountered when the air conditioner is abnormal. That is, even if an effort is made to communicate the air-conditioning abnormality signal to the drive system controller 304 through the air-conditioning communication line 318, such an abnormal state cannot be delivered to the drive system controller 304 because the air-conditioning signal is a drive information signal indicating that the air conditioner 310 is switched either on or off.
Therefore, the communication device 306 must conventionally be provided with a dedicated communication passage to indicate abnormalities in the air conditioner, i.e., the air-conditioning abnormality communication line 320, independent of the air-conditioning communication line 318. Accordingly, there is no choice but to communicate the presence of the abnormalities in the air conditioner 310 through the aforesaid communication line 320. This causes another inconvenience of more communication lines and higher cost.